Fluoroplastic silicone vulcanizates

Abstract

A method for preparing a fluoroplastic silicone composition is disclosed containing both a fluoroplastic and a cured organopolysiloxane using dynamic vulcanization techniques. A silicone compound containing a curable organopolysiloxane is first prepared, mixed with a fluoroplastic, and then cured via dynamic vulcanization.

1 . A method for preparing a fluoroplastic composition comprising: 
 (I) mixing 
 (A) a fluorocarbon resin having a glass transition temperature above 23° C.,  
 (B) a compatibilizer,  
 (C) an optional catalyst,  
   (II) mixing the product of step (I) with 
 (D) a silicone base comprising a curable organopolysiloxane,  
 (E) a radical initiator in an amount sufficient to cure said 
 organopolysiloxane; and  
 
   (III) vulcanizing the organopolysiloxane,    wherein the weight ratio of fluorocarbon resin (A) to silicone base (D) in the elastomeric base composition ranges from 95:5 to 30:70.    
   
   
       2 . The method of  claim 1  wherein the fluorocarbon resin (A) is a fluoroplastic homopolymer, copolymer, or terpolymer comprising monomers selected from the group of tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, and vinylidene fluoride monomers.  
   
   
       3 . The method of  claim 1  wherein the compatibilizer (B) is selected from the group of (B′) organic compounds which contain 2 or more olefin groups, (B″) organopolysiloxanes containing at least 2 alkenyl groups and (B′″) olefin-functional silanes which also contain at least one hydrolyzable group or at least one hydroxyl group attached to a silicon atom thereof.  
   
   
       4 . The method of  claim 1  wherein the compatibilizer (B) is a hydroxy end-blocked methyl vinyl siloxane.  
   
   
       5 . The method of  claim 1  wherein optional catalyst (C) is present and is an organic peroxide.  
   
   
       6 . The method of  claim 1  wherein the curable organopolysiloxane is a diorganopolysiloxane gum containing at least 2 alkenyl groups having 2 to 20 carbon atoms and having a sufficient molecular weight to impart a Williams plasticity number of at least 30 as determined by the American Society for Testing and Materials (ASTM) test method D 926.  
   
   
       7 . The method of  claim 1  wherein the radical initiator is an organic peroxide.  
   
   
       8 . The method of  claim 1  wherein the vulcanization of step (III) is a dynamic vulcanization.  
   
   
       9 . The method of  claim 8  wherein the dynamic vulcanization occurs via an extrusion process.  
   
   
       10 . The method of  claim 9  wherein the extrusion process occurs in a twin screw extruder.  
   
   
       11 . The method of  claim 1  wherein the vulcanization of step (III) is a static vulcanization.  
   
   
       12 . A fluoroplastic composition produced by the method of  claim 1 .  
   
   
       13 . An article of manufacture comprising the fluoroplastic composition of  claim 12.